Turbodrill



July 4, 1961 FIG.

J. A. MITCHELL ET AL TURBODRILL Filed Oct. 20, 1958 FIG. 4.

IN VEN TORS Unite VFiled Oct. 20, 1958, Ser.'No. 768,443 6 Claims. (Cl.175-107) The present invention relates to a turbodrill or duid driventurbine that is carried on the end of adrill string and, actuated by thedownowing drilling fluid, drives a rotary drill bit for the down-holedrilling of oil wells and the like.

Although the turbodrill has been known for a number of years, asevidenced by Cross Patent No. 142,992 issued in 1873, and WestinghousePatent No. `307,606 issued in 1884, it is only in very recent years thatthe basic turbodrill invention has advanced the turbodrill toward aVstate of commercial usage. There werevarious technical reasons for thedelay, such as the early development of direct rotary drilling which,following its` adoption around 11900, became the accepted procedure.Rotary drilling remains the standard procedure in this country and, fromthe standpoint of cost per foot of hole drilled, i-t has not as yet beencommercially superseded.

However, the early concepts of turbodrill operation and subsequentmodifications have led the inventively minded in Ythis eld to give agreat deal of consideration to the realization of the great economieswhich this form of drilling could afford. These are evident because inrotary drilling there may be as much as 90% energy loss due to thefriction of the rotary pipe in the bore hole. Moreover, the effect ofthe heavy loading on the bit, which now runs as much as 40,000 to100,000 pounds, not only requires very heavy drill collar sections, butunder many circumstances results in angular deviations in drilling thatexceed the permissible limits for well bore verticality. With areduction of load on the bit, there is an attendant reduction in rate ofpenetration and frequently supplemental equipment such as whipstocksmust be used to correct these deviations.

The use of a turbodrill has the distinct advantage over rotary drillingin that the driving torque is close to the bit. It utilizes the drillingiluid which is necessary for removing the cuttings `from the well and itcan be made of adequate power to permit rapid drilling. The direct drivemultiple stage type turbodrill does have a `somewhat higher rotationalspeed as compared to normal rotary operation, but with improved bits theturbodrill'can 'be expected `to drill considerably faster and cheaperthan -is possible with rotary drilling.

A turbodrill is, however, `a `down-hole engine which operates "in alluid-laden/well bore and the atmosphere of highly abrasive fluid standsin the way of any normal lubrication of the wear parts. Its limiteddiameter, which seldom exceeds twelve inches and is usually in the orderof six to eight inches, also limits the internal design be yond thatpossible with turbines used above ground.

One of the serious problems that has developed in the operation of suchturbodrills is a tendency of the high velocity, downwardly movingdrilling fluid to leak out through the bearings of the turbodrill and,due to this velocity effect, to erode the rock bit and to interfere withthe discharge of cuttings from the bore. Hence, one of the principallobjects of this invention is to overcome this grave problem ofeffectively protecting the rock bit against deterioration and to utilizethe forces to assist in clearing the bore. The nature of this problemand the means of its solution will be more fully understood from thefollowing detailed description kand a consideration of the accompanyingdrawings, in which:

FIG. 1 is an enlarged and partially longitudinally sectioned turbodrillshowing the lower portion of the turbo- States Patent O 2,990,894Patented July 4, 1961 ICC 2 drill housing and the depending drivingsha-ft and bit operatively positioned in the bore hole and resting onbottom;

FIG. 2` is a horizontal view of the turbodrill as shown in FIG. l, takenon line 2 2 thereof and showing the upper face of the mud deliector orbit protector means.

FIG. 3 is a gpartial vertical section taken on line 3--3 of FIG. 2 andshowing the meansfor securing the protector means in position; and pFIG.14 is also a partial vertical section of the lower end of the drillstring of FIG. 1, illustrating a modification of the protector meansshown in FIG.` 3.

As is well known in theY turbodrillart and as more particularly shown inthe copending application of Harn mer et al. led September 30, 1958,`Serial No. 764,213, the turbodrill is ay down hole mud driven turbinewhich is supplied with drilling iiuid which passes through from thedrill string through a series of rotor and stator blades and thence tothe drill bit. This drilling fluid then returns through the bore,clearing the cuttings and carrying them to a suitable sump from whichthe liquid can again be pumped down hole.

In a turbodrill of this type -it has been found that vfor a 65/a-inchnominal diameter turbodrill having approximately turbine stages, it isnecessary to pump down hole approximately 600 gallons per minute of mudto develop the desired drilling torque equivalent to about H.P. The mudpressure on the surface will range from 1,000 to 3,000 pounds per squareinch gauge.

As shown in FIG. l the lower portion of the rotating turbodrill shaft41, which is carried in the housing 40, is provided with suitable thrustbearing discs 42 alternately spaced with stationary bearing members 44which are carried by the housing to resist axial thrust in eitherdirection. These fixed bearing members have drilling fluid passages 45whereby the bearings are both cooled and lubricated. Most of thedrilling fluid then enters the central part of shaft 40 by port 45a.

"In addition to the thrust bearings we also provide ra radial bearingassembly, including a hardened sleeve 60 mounted on the shaft 41 andkeyed to it by the key 61. This bearing surface is engaged by theadjacent'cartridge and sleeve top bea-ring element 63 which is mountedin the turbodrill housing 64 and is lheld in place by vtheretainer ring65. The outer hardened surface sleeve 66 is customarily provided withfluid passages, which are shown as clearances on the drawing in FIG. land permit some of the drilling fluid to pass between the bearingsurface also for the purposes of cooling and lubrication.

It Vhas been found that with the high drilling uid pressure required toeffectively operate the turbine, there is some discharge from the bottomof the housing 64 and the shaft 41. In one instance it was found thatthe velocity of this discharge was in excess of 1,000 feet per minuteand served as a cutting jet which carried all the way to the shirttailof the rock bit 19, even to the point of cutting upon the back of theforgings and permitting the discharge of the balls from the ball races.-It also seriously alects the discharge of the cuttings from the borecausing such turbulence and erosion of the bit as to be criticallyobjectionable.

As more particularly disclosed in FIG. 1 and in FIG. 3, we have found itentirely satisfactory to install a deflector ring generally indicated at30 on the lower shaft 41 and below the bottom of the housing 64.

In the preferred form, the deilector ring 30 comprises a metallic ringformed with a continuous annular groove 32 on its upper surface, whichgroove is of V-shape in cross-section and relatively shallow, with eachdeecting Surfacey directed away from the other at an angle of the orderof 30 degrees from a normal.

This ring 30 has 3 an external diameter that is approximately equal tothat of the turbodrill housing 31.

As best shown in FIGS. Q and 3, the deflector ring 30 may be firmlysecured on the drill shaft 41 by a plurality ofperipherally spaced setscrews 34 countersunk within the ring. While it is ordinarily sufficientto secure the deliector ring 30 in position by means of such set screws,the impact forces thereon may become so great 'that it is necessary toprovide a recessed annular portion on the shaft to receive a key or snapring retaining means.

Use of the set screw securing means for the deliecting ring asillustrated in FIG. 3 may be eliminated entirely by the substitution fora metal ring a deformable resilient ring 36 of like shape made of rubberor plastic stretched over the Ilower drill shaft 41. It has beendetermined that when such a deflector ring 36 having a central bore oftwo and one-half inch diameter is stretched over a four-inch drillshaft, i.e. (41), it will maintain itself in operative fluid deflectingrelation without assistance. Even more positive retention of theresilient deflector ring may be obtained by providing an anular shaftrecess partially receiving the inner rim portion thereof.

From the explanation that has been given it will be understood that ajet (usually in the form of an annular curtain) of drilling uiddischarging from the casing will be intercepted and prevented fromstriking the bit. This of itself would be a valuable protection for thebit and is highly important. In addition, however, the jet or curtain ofthe mud laden drilling fluid is redirected upwardly where it becomescommingled with the upwardly moving drilling fluid, and positivelyaugments both the lifting force of the returning mud flow to the surfaceand the discharge of pressure Huid from the turbine.

In this manner indirect but very effective protection has been providedfor the drill bit 19 by preventing destructive erosion causing exposureof the bearings of the bit t well iiuid scouring.

Similar high velocity leakage from the turbine housing section 31containing a cartridge type bearing 63 will also be effectivelyminimized.

Thus it will be appreciated that the successful use of a turbodrill ofthe character described for practical periods of operation is largelydependent on the effective utilization of the deecting means in theassociation described herein.

Having thus described our invention and the best mode of `practicing thesame, what we claim as novel is:

1. In a mud-driven turbodrill for downhole drilling having a tubularhousing, a hydraulic turbine assembly in said housing including a shaftadapted yfor rotation with respect to the housing by the passage ofdrilling mud through the housing, a drill bit carried by the shaft, avradial bearing adjacent the end of the housing and between the housingand the shaft, said shaft having a main conduit for carrying muddischarged from the turbine assembly to the bottom of a hole to returncuttings to the surface of said hole, said bearing having a liquidleakage path from inside the housing to a location below and external ofthe housing to permit a portion of the drilling mud to pass across thebearing to cool and lubricate said bearing, and deector means mounted onsaid shaft beneath said housing and between the end of said housing andsaid bit, and of a diameter to intercept the mud discharging from saidhousing through said leakage path to prevent impingement of said mud onsaid bit, said deliector means having means on the upper surface thereofformed and arranged to redirect said leakage mud upward to aid the muddischarging from the bottom of the shaft lin lifting cuttings from thehole.

2. A turbodrill for drilling a well bore, said turbodrill comprising -atubular housing, a hydraulic turbine assembly in said housing andincluding a driven shaft, a rock bit adapted to be driven by said shaft,a radial bearing between the lower end of said tubular housing and saidshaft, said bearing being adapted to provide a downwardly directedliquid leakage path out of said housing and across said bearing,llaterally extending deflector means mounted on the shaft in encirclingrelation and positioned below the housing and above the bit to receivedownwardly flowing liquid leakage from said housing and redirect saidowing liquid upwardly between the tubular housing and the well bore soas to avoid scouring and destruction of the bit by the otherwisedownwardly directed liquid stream.

' 3. The combination of claim l in which the deilector means is alaterally extending ring detachably affixed to the shaft.

4. The combination of claim l in which the detlector means is an annularring with an upwardly directed V-shaped formation on its upper surface.

5. The combination of claim 1 in which a plurality of circumferentiallyspaced set screws secure the deflector means to the shaft.

6. The combination of claim 2 in which the deector means is an annularring having an upwardly directed continuous groove-shaped formation.

References Cited in the file of this patent UNITED STATES PATENTS1,663,025 Phipps Mar. 20, 1928 Y 1,786,173 Scharpenberg Dec. 23, 19301,999,662 Nell Apr. 30, 1935 2,095,725 Whealy Oct. 12, 1937 2,588,311Wagner Mar. 4, 1952 '2,710,741 Hall June 14, 1955 2,828,945 New Apr. 1,1958 FOREIGN PATENTS 26,451k Great Britain 1911

